The grain bite wounds and grain bite off of corn harvester snapping means caused a serious loss. Aiming at those existed problems, a polygonal vertical-rollers snapping means with simple structure, good snapping effect and high reliability was designed. The mechanism of the vertical vibration snapping broken was studied. And then the design methods of main structural parameters for polygonal vertical-rollers snapping means were analyzed. Orthogonal design method was used for test design with influence factors of the number of edges, snapping roll speed and snapping roll diameter. By orthogonal test, it can be known that the factors affecting the quality of snapping in order of their importance were the number of edges, snapping roll speed and snapping roll diameter. By orthogonal test, it can be known that the optimum combination was snapping roll diameter of 7cm, the number of edges of 8, snapping roll speed of 950r/min. Test under optimum combinations was carried out, and it was found that the grain broken rate was 0.13%, the grain loss rate was 0.28%, and the rate of broken stem was 0.53%. The grain losses and damages were both far lower than the national standard. Under optimum conditions, validation tests were done to determine the most appropriate size of the interior angle adjustment. The test result showed that the resizing interior angle Δ was 16°, which was half of the maximum interior angle range of adjustment, and under this conditions the harvesting quality was the best.